diff --git a/node.c b/node.c
index 1ea6cade20..050f8e4061 100644
--- a/node.c
+++ b/node.c
@@ -1042,7 +1042,7 @@ rb_node_init(NODE *n, enum node_type type, VALUE a0, VALUE a1, VALUE a2)
 
 typedef struct node_buffer_elem_struct {
     struct node_buffer_elem_struct *next;
-    NODE buf[FLEX_ARY_LEN];
+    NODE buf[1];
 } node_buffer_elem_t;
 
 struct node_buffer_struct {